Embodiments described herein relate to self propelled vehicles, particularly general delivery vehicles employed for local package delivery and pickup.
Parcel delivery vehicles have conventionally been built using body on frame construction. This style of construction has made heavy use of steel, with some use of lighter weight materials. The power plant and drive train layout has relied on an internal combustion engine configured in a front engine, rear wheel drive set up. The basic design emphasizes simplicity, ease of access to the engine and transmission for service and durability for stop and go driving in urban environments. The weight, aerodynamic attributes, particularly relating to engine cooling, and inflexibility in sizing have posed fuel economy issues for application of the design to hybrid or full electric drive vehicles.
For a conventional, internal combustion engine-equipped vehicle, the inherent relative inefficiency of the internal combustion engine compared to electric motors in terms of converting stored energy to vehicle motion means that economy gains from increasing the energy conversion efficiency of the power train may exceed gains obtained from improving aerodynamics or reducing weight. Internal combustion engines also exhibit much greater parasitic and idling losses than do electric motors. Electric motors are much more efficient than diesel and other internal combustion engines, converting over 90% of the input energy to motive power. In addition, electric motors are more easily adapted to regenerative braking. However, the batteries used to store energy to supply the electricity to vehicle fraction motor energy store at vastly lower densities, and at a much greater weight penalty, than does diesel fuel. As a consequence, electric vehicles have operated under tighter range constraints than diesel-engine equipped vehicles and the range of electric vehicles is much more sensitive to vehicle weight and aerodynamics than it is for diesel-engine equipped vehicles. Range issues can be addressed by adding battery capacity, but doing so takes up space that could be used for cargo, can raise the floor level of the vehicle, and adds still more weight to the vehicle. And unlike internal combustion engine-equipped vehicles which lose weight as fuel is consumed, a vehicle using batteries to store energy does not lose weight as stored energy is exhausted.